The UN has urged the Iraqi government to launch a probe into the attack on a military base in June.
"The UN's Special Representative for Iraq, Nickolay Mladenov, has called on the Iraqi authorities to conduct a public investigation into the attack at Camp Speicher when it was seized by the Islamic State (IS) militants June 12," Xinhua quoted spokesman Stephane Dujarric as saying Wednesday.
Mladenov said that evidence suggests that a massacre was committed at the camp and hundreds of Iraqis were killed by the IS.
The terrorist group claimed in June that it had executed some 1,700 captured soldiers and other military personnel from the camp.
In Baghdad, families and relatives of missing Iraqi soldiers from the camp broke into the parliament building Tuesday, accusing parliament of ignoring their demand to interrogate military commanders who are "responsible for the disappearance of their sons".
Mladenov has urged the Iraqi authorities to do all they can to uncover the truth, to locate and identify the remains of those killed, and to undertake efforts to secure the release of anyone still held in captivity.
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Camp Speicher, located north of Salahudin's provincial capital of Tikrit, was attacked in June when IS seized large areas of northern and north central Iraq.
In days after the capture, pictures and videos posted online by the IS showed horrendous scenes of a large number of young men being herded onto trucks, transported to a remote location, and then forced to lie on the ground in rows, as the militants systematically and brutally killed them.
The UN Human Rights Council passed a resolution Monday calling on the Office of the UN High Commissioner for Human Rights (OHCHR) to dispatch a team of investigators to Iraq to inquire into crimes committed by the IS and associated armed groups to ensure accountability.